AP Chemistry Practice Test #4
Chapter 6
1. A gas absorbs 0.0 J of heat and then performs 74.4 J of work. The change in internal energy
of the gas is
a.
b.
c.
d.
e.
34.4 J
74.0 J
114.4 J
-74.4 J
none of these
2. Of energy, work, enthalpy, and heat, how many are state functions?
a.
b.
c.
d.
e.
0
1
2
3
4
3. Which of the following statements correctly describes the signs of q and w for the following
exothermic process at P = 1 atm and T = 370 K?
H2O(g) → H2O(l)
a. q and w are negative.
b. q is positive, w is negative.
c. q is negative, w is positive.
d. q and w are both positive.
e. q and w are both zero.
4. One mole of an ideal gas is expanded from a volume of 1.00 liter to a volume of 6.53 liters
against a constant external pressure of 1.00 atm. How much work (in joules) is performed on
the surroundings? Ignore significant figures for this problem. (T = 300 K; 1 L atm = 101.3
J)
a.
b.
c.
d.
e.
280 J
560 J
1681 J
661 J
none of these
5. Which statement is true of a process in which one mole of a gas is expanded from state A to
state B?
a. When the gas expands from state A to state B, the surroundings are doing work on the
system.
b. The amount of work done in the process must be the same, regardless of the path.
c. It is not possible to have more than one path for a change of state.
d. The final volume of the gas will depend on the path taken.
e. The amount of heat released in the process will depend on the path taken.
6. Which one of the following statements is false?
a. The change in internal energy, ∆E, for a process is equal to the amount of heat absorbed
at a constant volume, qv.
b. The change in enthalpy, ∆H, for a process is equal to the amount of heat absorbed at
constant pressure, qp.
c. A bomb calorimeter measures ∆H directly.
d. If qp for a process is negative, the process is exothermic.
e. The freezing of waer is an example of an exothermic reaction.
Use the following to answer questions 7-11:
Consider a gas in a 1.0 L bulb at STP that is connected via a valve to another bulb that is initially
evacuated. Answer the following concerning what occurs when the valve between the two bulbs
is opened.
7. What is true about the value of q?
a.
b.
c.
d.
e.
It is greater than zero.
It is equal to zero.
It is less than zero.
More information is needed.
none of these
8. What is true about the value of ∆H?
a.
b.
c.
d.
e.
It is greater than zero.
It is equal to zero.
It is less than zero.
More information is needed.
none of these
9. What is true about the value of w?
a.
b.
c.
d.
e.
It is greater than zero.
It is equal to zero.
It is less than zero.
More information is needed.
none of these
10. What is true about the value of ∆E?
a.
b.
c.
d.
e.
It is greater than zero.
It is equal to zero.
It is less than zero.
More information is needed.
none of these
11. Two metals of equal mass with different heat capacities are subjected to the same amount of
heat. Which undergoes the smallest change in temperature?
a.
b.
c.
d.
e.
The metal with the higher heat capacity.
The metal with the lower heat capacity.
Both undergo the same change in temperature.
You need to know the initial temperatures of the metals.
You need to know which metals you have.
12. A 25.5 g piece of aluminum (which has a molar heat capacity of 24.03 J/oC mol) is heated to
82.4oC and dropped into a calorimeter containing water (specific heat capacity of water is
4.18 J/goC) initially at 22.3oC. The final temperature of the water is 24.9oC. Calculate the
mass of water in the calorimeter. Ignore significant figures for this problem.
a.
b.
c.
d.
e.
120.2 g
3242.0 g
3.64 g
1305.9 g
none of these
13. Consider a rigid insulated box containing 20.0 g of He(g) at 40.7oC and 1.00 atm in one
compartment and 20.0 g of N2(g) at 115.0oC and 2.00 atm in the other compartment. These
compartments are connected by a partition which transmits heat. What will be the final
temperature in the box at thermal equilibrium? (Cv(He) = 12.5 J/K mol, Cv(N2) = 20.7 J/K
mol)
a.
b.
c.
d.
e.
54.9oC
-218.1 oC
77.9oC
87.0oC
none of these
14. For a particular process q = -17 kJ and w = 21 kJ. Which of the following statements is
false?
a.
b.
c.
d.
e.
Heat flows from the system to the surroundings.
The system does work on the surroundings.
E = +4 kJ
The process is exothermic.
None of the above is false.
15. Calculate the work associated with the compression of a gas from 121.0 L to 80.0 L at a
constant pressure of 14.3 atm.
a.
b.
c.
d.
e.
-586 L atm
586 L atm
2.87 L atm
-2.87 L atm
101 L atm
16. In the lab, you mix two solutions (each originally at the same temperature) and the
temperature of the resulting solution decreases. Which of the following is true?
a.
b.
c.
d.
e.
The chemical reaction is releasing energy.
The energy released is equal to s x m x T.
The chemical reaction is absorbing energy.
The chemical reaction is exothermic.
More than one of these.
17. A 140.0-g sample of water at 25.0oC is mixed with 103.2 g of a certain metal at 100.0oC.
After thermal equilibrium is established, the (final) temperature of the mixture is 29.6oC.
What is the heat capacity of the metal, assuming it is constant over the temperature range
concerned?
a. 0.37 J/goC
b. 0.74 J/goC
c. 0.20 J/goC
d. 2.7 J/goC
e. none of these
18. For the reaction H2O(l) → H2O(g) at 298 K, 1.0 atm, ∆H is more positive than ∆E by 5
kJ/mol. This quantity of energy can be considered to be
a.
b.
c.
d.
e.
the heat flow required to maintain a constant temperature.
the work done in pushing back the atmosphere.
the difference in the H-O bond energy in H2O(l) compared to H2O(g).
the value of ∆H itself.
none of these
19. Consider the reaction
C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l) ∆H = -1.37x103 kJ
When a 24.8-g sample of ethyl alcohol (molar mass = 46.1 g/mol) is burned, how much
energy is released as heat?
a.
b.
c.
d.
e.
0.538 kJ
0.737 kJ
7.37e2 kJ
3.40e4 kJ
1.86 kJ
20. If 5.0 kJ of energy is added to a 15.5-g sample of water at 10.oC, the water is
a.
b.
c.
d.
e.
boiling.
completely vaporized.
frozen solid.
decomposed.
still a liquid.
21. The total volume of hydrogen gas needed to fill the Hindenburg was 2.00 x 108 L at 1.00 atm
and 24.5oC. How much energy was evolved when it burned?
∆H = -286 kJ
H2(g) + 1/2O2(g) → H2O(l)
a.
b.
c.
d.
e.
8.19e6 kJ
2.85e10 kJ
2.86e4 kJ
2.34e9 kJ
4.59e9 kJ
22. CH4 + 4Cl2(g) → CCl4(g) + 4HCl(g), ∆H = -434 kJ
Based on the above reaction, what energy change occurs when 1.2 moles of methane reacts?
a.
b.
c.
d.
e.
5.2 x 105 J are released.
5.2 x 105 J are absorbed.
3.6 x 105 are released.
3.6 x 105 are absorbed.
4.4 x 105 J are released.
23. Given the equation S(s) + O2(g) → SO2(g), ∆H = -296 kJ, which of the following
statement(s) is (are) true?
I.
II.
III.
a.
b.
c.
d.
e.
The reaction is exothermic.
When 0.500 mole sulfur is reacted, 148 kJ of energy is released.
When 32.0 g of sulfur are burned, 2.96 x 105 J of energy is released.
All are true.
None is true.
I and II are true.
I and III are true.
Only II is true.
24. When 0.239 mol of a weak base (A-) is reacted with excess HCl, 6.91 kJ of energy is released
as heat. What is ∆H for this reaction per mole of weak base consumed?
a.
b.
c.
d.
e.
-34.6 kJ
-1.65 kJ
-28.9 kJ
34.6 kJ
28.9 kJ
25. A 3.7-g sample of Colorado oil shale is burned in a bomb calorimeter, which causes the
temperature of the calorimeter to increase by 5.0oC. The calorimeter contains 1.00 kg of
water (H2O = 4.184 J/goC) and the heat capacity of the empty calorimeter is 0.10 kJ/oC. How
much heat is released per gram of oil shale when it is burned?
a.
b.
c.
d.
e.
21 kJ/g
42 kJ/g
0 kJ/g
5.8 kJ/g
0.17 kJ/g
26. Consider the following processes:
2A → 1/2B + C
(3/2)B + 4C → 2A + C + 3D
E + 4A → C
Calculate ∆H for: C → E + 3D
a.
b.
c.
d.
e.
∆H1 = 5 kJ/mol
∆H2 = -15 kJ/mol
∆H3 = 10 kJ/mol
0 kJ/mol
10 kJ/mol
-10 kJ/mol
-20 kJ/mol
20 kJ/mol
27. Which of the following does not have a standard enthalpy of formation equal to zero at 25oC
and 1.0 atm?
a.
b.
c.
d.
e.
F2(g)
Al(s)
H2O(l)
H2(g)
They all have a standard enthalpy equal to zero.
28. At 25oC, the following heats of reaction are known:
∆H (kJ/mol)
2ClF + O2 → Cl2O + F2O
167.4
2ClF3 + 2O2 → Cl2O + 3F2O
341.4
2F2 + O2 → 2F2O
-43.4
At the same temperature, calculate ∆H for the reaction: ClF + F2 → ClF3
a.
b.
c.
d.
e.
-217.5 kJ/mol
-130.2 kJ/mol
+217.5 kJ/mol
-108.7 kJ/mol
none of these
29. Given the following two reactions at 298 K and 1 atm, which of the statements is true?
1.
N2(g) + O2(g) → 2NO(g)
∆H1
∆H2
2.
NO(g) + (1/2)O2(g) → NO2(g)
a.
b.
c.
d.
e.
∆Hof for NO2(g) = ∆H2
∆Hof for NO(g) = ∆H1
∆Hof = ∆H2
∆Hof for NO2(g) = ∆H2 + (1/2) ∆H1
none of these
Cu2O(s) + (1/2)O2(g) → 2CuO(s)
∆Ho = -144 kJ
∆Ho = +11 kJ
Cu2O(s) → Cu(s) + CuO(s)
Calculate the standard enthalpy of formation of CuO(s).
30. Given:
a.
b.
c.
d.
e.
-166 kJ
-299 kJ
+299 kJ
+155 kJ
-155 kJ
31. The heat combustion of acetylene, C2H2(g), at 25oC, is -1299 kJ/mol. At this temperature,
∆Hof values for CO2(g) and H2O(l) are -393 and -286 kJ/mol, respectively. Calculate ∆Hof
for acetylene.
a.
b.
c.
d.
e.
2376 kJ/mol
625 kJ/mol
227 kJ/mol
-625 kJ/mol
none of these
32. Using the following data, calculate the standard heat of formation of the compound ICl in
kJ/mol:
∆Ho (kJ/mol)
242.3
Cl2(g) →2Cl(g)
I2(g) → 2I(g)
151.0
ICl(g) → I(g) + Cl(g)
211.3
I2(s) → I2(g)
62.8
a.
b.
c.
d.
e.
-211 kJ/mol
-14.6 kJ/mol
16.8 kJ/mol
245 kJ/mol
439 kJ/mol
33. On a cold winter day, a steel metal fence post feels colder than a wooden fence post of
identical size because
a. the specific heat capacity of steel is higher than the specific heat capacity of wood.
b. the specific heat capacity of steel is lower than the specific heat capacity of wood.
c. steel has the ability to resist a temperature change better than wood.
d. the mass of steel is less than wood so it loses heat faster.
e. Two of the above statements are true.
34. Which of the following statements is/are true?
I.
q(heat) is a state function because ∆H is a state function and q = ∆H.
II.
When 50.0 g of aluminum at 20.0oC is placed in 50.0 mL of water at 30.0oC, the
H2O will undergo a smaller temperature change than the aluminum. (The density
of H2O = 1.0 g/mL, specific heat capacity of H2O = 4.18 J/oC g, specific heat
capacity of aluminum = 0.89 J/oC g)
III.
When a gas is compressed, the work is negative since the surroundings is doing
work on the system and energy flows out of the system.
IV.
For the reaction (at constant pressure) 2N2(g) + 5O2(g) → 2N2O5(g), the change in
enthalpy is the same whether the reaction takes place in one step or in a series of
steps.
a.
b.
c.
d.
e.
I, II, IV
II, III
II, III, IV
II, IV
All of the above statements are true.